| Pharmaceutical wastewater often contains high concentration non-biodegradable organic compounds, the discharge of toxic substances not degraded in pharmaceutical wastewater cause serious detrimental effect to the natural environment. Therefore, supported by the "Eleventh Five-Year" National Water Pollution Control Projects (Hun river in Liaoning province, China), we were committed to investigate the integration process in treating fosfomycin pharmaceutical wastewater from Northeast General Pharmaceutical Factory, using catalytic wet air oxidation (CWAO) and aerobic granular sludge which used struvite granule formed by precipitative phosphate removal.In CWAO treatment of fosfomycin pharmaceutical wastewater, WO3-and PO43-(converted from fosfomycin calt oxidation) in fosfomycin wastewater and Cu2+(generated from decoppering) in berberine pharmaceutical wastewater could form Cu2+[PxWmOy]q-, namely polyoxometalates (POMs). At250℃and1.4MPa initial oxygen pressure,41%and43%of COD (chemical oxygen demand, the initial COD of mixed streams was121081mgL-1) and TOC (total organic carbon, the value of mixed streams was5823mgL-1) removal can be easily realized, meanwhile,95%organophosphorus and70%organic amine were converted to PO43-and NH4+,respectively. The biodegradability of wastewater was enhanced by the CWAO treatment. In addition, fosfomycin was incompletely oxidized to propionic acid or propanol, and the resolving agent phenethylamine was oxidized to benzoic acid. Noteworthy, reusing these active ions and detoxicating organophosphorus simultaneously, satisfies the demand of "treating wastes with other wastes". Both the hydroxyl radical reaction and catalytic oxidation play crucial roles in the CWAO process. Supersaturated precipitate Cu2+[PxWmOy]q-can be easily separated from the effluent, which can reduce secondary pollution caused by heavy metal ions used in CWAO. Characterizations(e.g., TGA, IR, XRD, XRF) and analysis of Cu2+[PxWmOy]q-showed that it was similar to P4W8O32in structure, and had high thermal stability, low microbial toxicity, and adjustable acid-base and redox properties.NH4+and PO43-in CWAO effluent can been removed simultaneously using precipitation method by forming magnesium ammonium phosphate (MgNH4PO4, MAP, struvite). Cu2+impurities can affect crystallization by entering into the crystal lattice or adsorbing on struvite surface. When Cu2+concentration was low,48%of PO43-was removed in the form of struvite.Struvite was reused as a carrier to cultivate aerobic granules and enhance the biological treatment. In start-up period, its addition stimulated polysaccharides generation (42.2mgg-1MLVSS versus28.4mgg-1MLVSS in sludge without it), which possibly caused accelerated granulation via the solid surface effect, compressed "double layer" effect by Mg2+and enriched ammonia-oxidizing bacteria (AOB) by free ammonia. The size of mature granules ranged from700to1100μm after30days cultivation. According to SEM and FISH analysis, AOB was found as the dominate strains over nitrite-oxidizing bacteria (NOB) and polyphosphate accumulating bacteria (PAO). Although the CWAO treated pharmaceutical wastewater contains toxic substance, the removal of90%COD and more than70%NH4+-N, was achieved the granule has significant nitrification effect, the average value of stable accumulation of nitrite was89%[NO2--N:(NO2--N+NO3--N)] in this biological treatment unit. This emphasizes that adding struvite as a new-type carrier can effectively promote the formation of partial nitrification granular sludge, and the new granular cultivation method is effective for cultivating nitrification granular sludge. |
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